This invention relates in general to radar systems and more particularly to a MTI radar system capable of determining the presence of moving targets while further providing vehicle identification.
A primary object of any radar employing moving-target indication (MTI) is to present to the user signals in a manner that moving targets will show up, while stationary objects give no response. MTI systems have been in widespread use and many such prior art devices employed a pulsed radar system in conjunction with a plan-position indicator (PPI) display. See, for example, a text entitled "Radar System Engineering" edited by Louis N. Ridenour, Volume I of Massachusetts Institute of Technology (Radiation Laboratory Series), Chapter 16 entitled MOVING-TARGET INDICATION.
Basically, the method of reception employed in a MTI system utilizes the well known doppler effect to determine target movement. The systems employed in the prior art can also furnish range information by modulating or chopping the transmitted signal and relying on the fact that stationary targets exhibit constant phase from pulse to pulse and therefore a steady amplitude as compared to the varying phase and amplitude of moving targets.
There exists a number of general descriptions and mathematical analysis of the characteristics of MTI systems as well as system operation. See, for example a text entitled AIRBORNE RADAR by Donald J. Povejsil, et al. published in 1965 by Boston Technical Publishers, Inc., pages 269 to 272.
In spite of the progress made in developing more sophisticated radar systems and display techniques, an outstanding problem in MTI radar is the tactically important ability of the system to discriminate between wheeled and tracked vehicles or to distinguish, for example, between a conventional automobile or jeep and a tank.
Trained operators, when employing aural detection, can identify tracked vehicles via the Doppler return only under special circumstances. These dictate illumination of the target by the transmitter at predetermined angles for receiving large return signals from the tracks, while maintaining a high signal to noise ratio.
If one uses a multiple doppler channel system, then each return channel is associated with a separate operator and the above technique is highly impractical. As is understood, the prior art schemes depend greatly upon the ability and discretion of the operator. Thus, the determination or discrimination between a tank and a jeep becomes at best an educated guess.
It is therefore an object of the present invention to provide a MTI radar system capable of reliably discriminating between wheeled and tracked vehicles by providing improved automatic detection circuits.